After the 9/11 terrorist attacks, "Pakistan was to be a key ally in combating Islamist militancy, becoming a leading recipient of US aid in the nearly 15 years since," Ed Royce (R-CA), the Republican chairman of the House Foreign Affairs Committee, said on Wednesday.

"But while the US was quick to embrace Pakistan-Pakistan has hardly reciprocated," he said in his opening statement at the hearing on "The Future of US-Pakistan Relations."

"Pakistani governments have come and gone, but Pakistan has remained a terrorist haven, with its security services supporting what it considers to be 'good' Islamist terrorist groups," Royce said.

Royce said his Panel "has repeatedly urged Pakistan to take meaningful action against key Islamist terrorist groups operating within its territory."

"Unfortunately Pakistan, which is now home to the world's fastest growing nuclear weapons programme, has remained a fount of radical Islamist thought."

Royce said he doubted "anyone who follows Pakistan closely was surprised to learn that one of the San Bernardino attackers - Tashfeen Malik - studied at a Pakistani school spreading a particularly conservative message."

Testifying before the panel Richard G. Olson, Special Representative for Afghanistan and Pakistan, said while Pakistan has made "significant sacrifices" in its fight against terrorism, "it can also take more steps to put pressure on all terrorist groups in Pakistan."

The US, he said, continued "to press Pakistan to target all militant groups that have safe haven in Pakistan, particularly the Taliban, including the Haqqani Network, and Lashkar-e-Taeba," held responsible for the Nov 26, 2008 Mumbai terror attack.

"We have made it clear to the Pakistanis that these organizations threaten Pakistan, the region, and the panoply of our mutual national security interests, and they must be addressed rigorously," Olson said.

It was "also critical that Pakistan improve relations with its other neighbour, India," he said expressing the hope the recent high-level talks between Indian and Pakistani officials "will be used to reduce tensions and increase ties between the two nations."